The Mitigation System of the Large Angle Foil Scattering Beam Loss caused by the Multi-turn Charge-exchange Injection

Abstract

In the J-PARC 3GeV rapid cycling synchrotron (RCS), the beam losses caused by the large-angle scattering of the both injected and circulating beams at the chargeexchange foil were observed downstream of the injection point. To realize high power operation, these losses had to be mitigated or localized in terms of exposure to radiation. Therefore, a new collimation system was developed and installed in the 2011 summer shutdown. In the beam commissioning at 181 MeV injection energy, these uncontrolled beam losses were successfully localized. Since the injection energy has been upgraded to 400 MeV in 2013 summer-autumn maintenance period, the readjustment of the collimator was performed. In this paper, the collimation system is introduced and the adjustment results are reported.